Artificial lighting systems for closed environments often aim at improving the visual comfort experienced by users. In particular, lighting systems are known which imitate natural lighting, specifically sunlight illumination, in particular using light with a high correlated color temperature (CCT), and a large color rendering index (CRI). The characteristics of such outdoor lighting to be imitated depend on the interaction between the sunlight and the earth atmosphere and create a specific shade characteristic.
The following disclosure is at least partly based on specific nanoparticle based Rayleigh-like scattering units, and their application in the field of active illumination such as in lighting in general. However, the generic concept may also be applicable to other embodiments of sun imitating lighting systems.
Using Rayleigh-like diffusing layers, several applications such as EP 2 30 478 A1, EP 2 304 480 A1, and WO 2014/076656 A1, filed by the same applicants, disclose lighting systems that use a light source producing visible light, and a panel containing nanoparticles used in transmission, i.e. the light source and the illuminated area are positioned on opposing sides of the panel. During operation of those lighting systems, the panel receives the light from the light source and acts in transmission as a so-called Rayleigh diffuser (herein also generally referred to as Rayleigh panel or briefly panel), namely it diffuses incident light similarly to the earth atmosphere in clear-sky conditions. Specifically, the concepts refer to directional light with lower correlated color temperature (CCT), which corresponds to sunlight, and diffused light with larger CCT, which corresponds to the light of the blue sky.
In general, for sun imitating lighting systems, an installation needs to provide for a sun-like beam extending—like the sun—in a top to bottom direction. As a consequence, the requirement of a sky-imitating at the ceiling results in space being needed for the lighting system behind the ceiling and, thus, affecting the bottom to ceiling parameters of a building/room.
Therefore, it is an object of the herein disclosed concepts to provide for sun imitating lighting systems that are less demanding on space and still provide for the visual comfort desired by users from lighting systems imitating natural lighting conditions. A further object of the herein disclosed concepts is to provide for an extended sky perception provided by lighting systems imitating natural lighting conditions.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.